(a) Field of the Invention
The present invention relates to a screen means in which a Fresnel lens is arranged in the proximity of a screen surface.
(B) Description of the Prior Art
As a high-resolution screen means, a screen means in which a Fresnel lens is arranged in the proximity of the screen is known. By such screen means, the light projected onto the screen is collected toward the observer and, therefore, it is possible to prevent the loss of brightness of the image projected onto the screen and to observe a bright image. For the Fresnel lens, it is known that the section of Fresnel surface is dentate and, therefore, the light is complicately reflected and refracted by respective surfaces of Fresnel lens and causes ghost images. As a method for eliminating the ghost images, it may be considered to arrange the back surface of the Fresnel lens as a frosted surface so that the reflected light is scattered by the frosted back surface. By the above method, it is possible to eliminate the ghost images to some extent. When, however, the Fresnel lens is made of plastic such as acrylic resin, flaws such as scratches will be caused to the Fresnel lens at the time of frosting work. It may be considered to form the frosted back surface directly by a mold when forming the Fresnel lens. As, however, it is impossible to use a release agent, the Fresnel lens will be bent when it is separated from the mold.